1. Field of the Invention
The present is related to a projection system in lithography system.
2. Background Art
In lithography systems, pattern generators are used to pattern substrates during an exposure process. Example lithography systems include, but are not limited to, reflective or transmissive maskless, immersion, and mask-based systems. Example substrates (e.g., work pieces) include, but are not limited to, semiconductor wafers, flat panel display substrates, flexible substrates, and the like. Light interacting with an illumination spot on the pattern generator become patterned. The patterned light is projected using a projection optical system onto one or more target areas of the substrate during the exposure process to form features on a photosensitive material (e.g., a photoresist) on the substrate.
Unfortunately, non-uniformity of a surface of the pattern generator, the substrate, and/or optics associated with the projection system can cause local magnification and/or focus errors, resulting in errors in patterns being formed on the substrate. As glass substrates grow larger and larger with each new generation of flat panel display produced therefrom, it becomes increasingly difficult to have flat and uniform thickness across the glass substrate. Also, as stages become larger to hold the large glass substrates, it become increasingly difficult to maintain the flatness of the substrate stage. Another cause of magnification errors can be temperature variation. Any one or more of these factors contribute to focus and/or magnification error.
Therefore, what is needed is a system and method that can be used to for local magnification errors and/or focus errors caused by non-compensate uniformity of a surface of a pattern generator, a substrate, and/or an optical element in at least a projection system of a lithography system.